Agronomic basics still key for Mid-South soybean growers

Too often Mid-South soybean producers aren't given enough information about basic agronomic practices, said David Lanclos at the recent Terral field day in Greenville, Miss.

Attempting to streamline basic agronomics and integrated pest management (IPM), the LSU AgCenter soybean specialist spoke on seeding rates, planting depths, seedling populations and variety selection. But there was a twist: Lanclos went through the season backwards.

Desiccants

After a survey of soybean specialists in the Mid-South, it was determined that 30 to 35 percent of Mid-South soybeans are receiving a desiccant of some type.

What type of desiccant is best? “I don't have a dog in the fight, but I do have a preference between sodium chlorate, Aim and paraquat. My preference is paraquat. I'm not a big fan of sodium chlorate. The stars have to be lined up just right to get it to work effectively.

“Some in Mississippi use a half-rate of both products and it works effectively. But my preference is paraquat, because it works regardless of conditions.”

More research — chiefly by LSU AgCenter professor Jim Griffin — has been done on application timing than rates. That's simply because “our recommendation in the past has been a moving target. Over the last couple years, you might have called me and asked the optimal time to desiccate the soybean crop. I'd have told you it's a moving target somewhere between 60 and 70 percent natural defoliation.

“But your 60 to 70 percent might be a lot different than mine. So, we've initiated research to get a (more precise) answer.”

Indeterminate soybeans include Group 3s and Group 4s. They begin flowering at the bottom of the plant and work up. The most juvenile seedpods will be at the top four or five nodes.

On determinate soybeans, the flowering begins in the middle and proceeds up and down the plant. “That's why there's a bit of a discrepancy in the recommendation between Group 4s and Group 5s. There's a lot more flexibility with the 4s.

“Bottom line is when you reach R-6.5 (when the seed is physically separated within the pod) total dry weight has been achieved and yield potential has been set. I prefer to see application a bit later.

“Growth stage-wise, the optimum time is at R-7.5 (when any of the pods at the upper four nodes easily shell into your hand).”

Fungicides

In the Mid-South, fungicide use is increasing every year. With the advent of Asian soybean rust in 2004, consultants and producers are looking at soybeans with more scrutiny than in the past decade.

“The number of calls we get reflects how hard everyone is scouting this crop. That's all positive. When people are looking at a crop, we'll be able to detect problems earlier.”

The use of fungicides is increasing because “data support that if you apply a strobilurin-based product such as Quadris or Headline at R-3, yields can be increased from 2 to 6 bushels per acre. It usually isn't less than 2 bushels and, in certain situations, it sometimes can be a lot more the 6 bushels. We've had some fields (increase yields) as much as 10 or 11 bushels.”

Lanclos calls the R-3 application the “money shot” because it's the one treatment in the absence of ASR that you don't want to miss. “It's the one that will make the most dividends.”

Insecticides

A newer insecticide, Syngenta's Endigo ZC, has been labeled in Louisiana. In Mississippi and Arkansas, “I'm told 24-Cs are being sought.”

Endigo ZC is a combination of Centric and Karate. Lanclos is “very optimistic about the product and LSU entomologists are rather high on it, as well. The reason I'm big on it is we've been using Orthene excessively.”

Orthene has been an “exceptional” product for control of Mid-South stink bugs. “But anytime we can welcome new chemistries to the market to control that complex, we'll support it. It's good anytime we can rotate crops and chemicals to deal with a pest.”

The Endigo ZC use rate is 4.5 ounces per acre (9 ounces per year) and it must be used in rotation with another product. “If you go with Orthene first, follow with Endigo ZC. But if you spray again, you need to use Orthene again. You can't use them simultaneously back-to-back.”

It's important to control the stink bug complex at certain reproductive growth stages. Matt Baur, LSU AgCenter research entomologist, has conducted much research on controlling stink bugs between R-3 and R-5 (pod initiation all the way to beginning seed-fill on any of the uppermost four nodes).

“Boiled down, the data says if you don't control stink bugs at high threshold to full threshold (six per 25 sweeps), yield losses will range from 3 percent to 45 percent per acre. That is potentially a severe hit — almost half your crop could be lost if left untreated. Stink bugs must be controlled.

“The take-home message is R-5 is more sensitive than R-4. And R-4 is more sensitive than R-3. It is absolutely imperative we do effective scouting and control for that insect complex.”

Beds

On the agronomic side, Lanclos spoke on the raised-bed/narrow-row system.

“Essentially, the beds can be raised to any height. (Louisiana) sugarcane beds are very large — 72 inches wide and almost a foot tall. But there are modifications to that. Many producers raise beds 2 inches to 4 inches.”

In general, “I think anytime you raise a bed and narrow row-spacing, it's a good thing. As we look at the way soybean production is going in the Mid-South, I think in 10 to 15 years as equipment changes, we'll see a lot more raised-bed/narrow-row beans. That's because the producers doing it are consistently cutting 50 to 60 bushels per acre.”

Is that the only reason they're getting such yields? “By no means. But it definitely benefits yields.”

The benefits are two-fold: narrowing rows spacing increases yields in general and also reduces stress from a moisture standpoint. “Reducing the stress of drainage is critical because beans don't like wet feet. If they stay wet, they stress and will go backwards. And once a bean crop goes backwards, there's not much to help turn it around.”

Regardless, by using the system, water will run off the fields a lot faster. And in adverse conditions, the field will be able to maintain moisture a bit longer.

Last year, Trey Koger compared a 40-inch and an 80-inch raised bed system to a flat system. Data showed a 5-bushel and a 7-bushel bump in the raised beds over the flat.

Koger, cotton weed scientist/agronomist at the Delta Research and Extension Center in Stoneville, Miss., also studied row spacing. “He compared a 10-inch, a 20-inch and a twin-row to a 40-inch, conventional bedding system. The 10-inch, 20-inch and twin-row had yields 9 percent higher than the 40-inch.”

Planting dates

His information on planting dates is specifically for Louisiana, warned Lanclos. “If your objective in Louisiana is to maximize Group 3 or Group 4 soybean yield potential, focus on April 10 to April 15. There are volumes of data to back this up.”

Can soybeans be successfully planted earlier? “Absolutely and I won't argue with a man wanting to do that. But I can say his yield potential won't be maximized.

“One interesting thing happening is the movement of Group 5s earlier and earlier. Right now, the earliest recommended planting date for a Group 5 is April 25.”

Over the last couple of years — stemming from Group 5s doing so well in extremely early-planted ASR sentinel plots — “we've looked at early Group 5s. I'm not recommending you plant one very early, but we are beginning to gather information on stunting and yield potential. In the future, we may get a lot more aggressive with planting date recommendations for Group 5s.”

Variety selection

In such volatile market conditions, variety selection is becoming much more serious for producers. “Recent growing seasons have been too wet, too dry. We haven't had a normal growing season in a while. When factoring that into variety selection, you must choose something bred and screened in the Mid-South. That's a must.”